Cylindrical battery

ABSTRACT

A cylindrical battery with an opening sealing body which includes a valve member, a metal plate disposed on an inner side of the battery with respect to the valve member, and an annular insulating member interposed between the valve member and the metal plate. The valve member and the metal plate are connected at respective central portions. The metal plate and the insulating member each have communicating holes. The valve member has a thin-walled portion which is deformable when an internal pressure of the battery increases. The insulating member has a section that covers a surface, on the valve member side, of the metal plate, a section that is provided subsequent to the section and covers a circumferential end face of the metal plate, and a section that is provided subsequent to the section and covers a surface, on an inner side of the battery, of the metal plate.

TECHNICAL FIELD

The present invention relates to a cylindrical battery.

BACKGROUND ART

A general cylindrical battery includes an electrode group, an electrolyte, a battery can that houses the electrode group and the electrolyte, and an opening sealing body that seals an opening of the battery can. The opening sealing body includes a valve member, a metal plate disposed on the inner side of the battery with respect to the valve member, and an annular insulating member interposed between the valve member and the metal plate (see PTL 1). The valve member and the metal plate are connected to each other at respective central portions. The valve member has an annular thin-walled portion which is deformable when the battery internal pressure increases. The above-mentioned opening sealing body includes a current cut-off mechanism.

Hereinafter part (an insulating member and a metal plate) of an opening sealing body used in a conventional cylindrical battery will be described with reference to FIG. 8.

As illustrated in FIG. 8, an insulating member 54 has a section P1 that covers the surface, on the valve member side (the battery outer side), of a metal plate 13, a section P2 that is provided subsequent to the section P1 and covers the circumferential end face of the metal plate 13, and a hook portion 55 that is provided subsequent to the section P2 and covers the surface, on the inner side of the battery, of the metal plate 13.

The metal plate 13 is stacked on the insulating member 54 which has been separately produced in advance, and the end of the metal plate 13 is inserted in between the section P1 of the insulating member 54 and the hook portion 55. In this manner, the metal plate 13 is fixed to the insulating member 54. In consideration of ease of insertion of the end of the metal plate 13 in between the section P1 and the hook portion 55, the hook portion 55 has been provided so as to cover the area less than 0.1 mm from the circumferential end face of the surface, on the inner side of the battery, of the metal plate 13 toward the center.

CITATION LIST Patent Literature

PTL 1: WO 2016/157749

SUMMARY OF INVENTION

However, at the time of battery crush by pressure, the opening sealing body is deformed, thus the end of the metal plate may be released from the hook portion, and the metal plate may come off from the insulating member. Due to a battery crush and coming off of the metal plate from the insulating member caused by the battery crush, the metal plate may come into contact with the battery can or the electrode group, and an internal short circuit may occur.

In consideration of what has been described above, an aspect of the present invention relates to a cylindrical battery including: an electrode group; an electrolyte; a battery can that houses the electrode group and the electrolyte; and an opening sealing body that seals an opening of the battery can, the opening sealing body including a valve member, a metal plate disposed on an inner side of the battery with respect to the valve member, and an annular insulating member interposed between the valve member and the metal plate, wherein the valve member and the metal plate are connected to each other at respective central portions, the valve member has a thin-walled portion which is deformable when an internal pressure of the battery increases, the insulating member has a section P1 that covers a surface, on the valve member side, of the metal plate, a section P2 that is provided subsequent to the section P1 and covers a circumferential end face of the metal plate, and a section P3 that is provided subsequent to the section P2 and covers a surface, on an inner side of the battery, of the metal plate, and the section P3 is provided to cover an area greater than or equal to 0.2 mm from the circumferential end face of the surface, on the inner side of the battery, of the metal plate toward a center.

According to the present invention, it is possible to control coming off of the metal plate from the insulating member, and an internal short circuit caused thereby at the time of battery crush by pressure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical cross-sectional view of a cylindrical battery according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an opening sealing body of FIG. 1.

FIG. 3 is a vertical cross-sectional view of a composite body of FIG. 2.

FIG. 4 is a plan view of the composite body of FIG. 2.

FIG. 5 is a back view of the composite body of FIG. 2.

FIG. 6 is a vertical cross-sectional view illustrating a modification of the composite body of FIG. 2.

FIG. 7 is a vertical cross-sectional view of a composite body used in a cylindrical battery according to another embodiment of the present invention.

FIG. 8 is a vertical cross-sectional view illustrating part of an opening sealing body used in a conventional cylindrical battery.

DESCRIPTION OF EMBODIMENTS

A cylindrical battery according to an embodiment of the present invention includes an electrode group, an electrolyte, a battery can that houses the electrode group and the electrolyte, and an opening sealing body that seals an opening of the battery can. The opening sealing body includes a valve member, a metal plate disposed on an inner side of the battery with respect to the valve member, and an annular insulating member interposed between the valve member and the metal plate. The valve member and the metal plate are connected to each other at respective central portions. The valve member has a thin-walled portion which is deformable when an internal pressure of the battery increases. The insulating member has a section P1 that covers a surface, on the valve member side (the battery outer side), of the metal plate, a section P2 that is provided subsequent to the section P1 and covers a circumferential end face of the metal plate, and a section P3 that is provided subsequent to the section P2 and covers the surface, on an inner side of the battery, of the metal plate. The section P3 is provided to cover an area greater than or equal to 0.2 mm from the circumferential end face of the surface, on the inner side of the battery, of the metal plate toward a center. In other words, a radial length L1 (hereinafter simply referred to as a length L1) of the area where the surface, on the inner side of the battery, of the metal plate is covered by the section P3 is greater than or equal to 0.2 mm.

In general, in consideration of ease of insertion of the end of the metal plate in between the section P1 and the hook portion (section P3), the length L1 has been less than 0.1 mm. However, at the time of battery crush by pressure, the metal plate may come off from the insulating member due to deformation of the opening sealing body, and thus the metal plate may come into contact with the battery can or the electrode group, and an internal short circuit may occur.

Thus, the inventors intensively discussed about the length L1. As a consequence, the inventors have newly valve member overed that when the length L1 is greater than or equal to 0.2 mm, the metal plate is stably fixed to the insulating member, and it is possible to control coming off of the metal plate from the insulating member due to deformation of the opening sealing body at the time of battery crush by pressure, and an internal short circuit (contact between the metal plate and the electrode group or the battery can) caused thereby.

However, when the length L1 is greater than or equal to 0.2 mm, it is difficult to insert the metal plate between the section P1 and the section P3 of the insulating member. To cope with this, the metal plate can be easily fixed to the insulating member with the length L1 greater than or equal to 0.2 mm by using, for example, the later-described insert molding technique. The length L1 is preferably greater than or equal to 0.3 mm, and more preferably greater than or equal to 0.4 mm. The section P3 may be annular, and may be provided at intervals along the circumferential direction of the metal plate.

The insulating member is produced using a general molding technique. The insulating member is preferably produced integrally with the metal plate by an insert molding among all. The insulating member and the metal plate can be bonded by an insert molding without using an adhesive agent. The insulating member integrated with the metal plate can be produced, for example, by loading a metal plate into a predetermined mold, and injecting a molten resin into the mold. By using an insert molding technique, the insulating member can be obtained integrally with the metal plate and the surface, on the valve member side, of the metal plate and the area from the circumferential end face of the metal plate to the surface, on the battery inner side (the opposite side to the valve member), of the metal plate can be easily covered by the insulating member. In other words, subsequent to the section P1 and the section P2, the section P3 can be easily provided. Also, the length L1 can be easily controlled at 0.2 mm or longer with an improved yield.

When the insulating member is produced integrally with the metal plate by an insert molding technique, the process of inserting the end of the metal plate in between the section P1 and the section P3 can be omitted, and the length L1 can be increased as compared with when the end of the metal plate is inserted in between the section P1 and the section P3.

Also, because of the integration of the insulating member with the metal plate, the thicknesses of the metal plate and the insulating member can be reduced, and accordingly the size of the electrode group can be increased and a higher capacity thereof can be aimed.

The insulating member includes a resin which can ensure the insulating property, and does not affect to the battery characteristics. The insulating member may further include a filler such as glass fiber. Resins used as the insulating member include, for example, polypropylene (PP), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyamide (PA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). The resins used as the insulating member are preferably PP and PBT among all from the viewpoint of cost advantage, superior heat resistance, and ease of integration with the metal plate by an insert molding.

The metal plate and the insulating member preferably have respective holes which communicate with each other. In this case, when the battery internal pressure increases, the valve member can reliably receive the pressure through the holes provided in the metal plate and the insulating member, and a current cut-off mechanism operates stably. The holes of the metal plate are provided in the area other than the central portion (the connection portion with the valve member) of the metal plate.

It is preferable that multiple (for example, two to 12, preferably four to eight) holes of the metal plate and the insulating member be provided along the circumferential direction of the metal plate and the insulating member. In this case, when the battery internal pressure increases, the thin-walled portion of the valve member is likely to receive the battery internal pressure uniformly in the circumferential direction.

Furthermore, the area from the lateral sides of the holes of the metal plate to the surface, on the inner side of the battery, of the metal plate may be covered by the insulating member. Specifically, the later-described P4 to P6 may be further provided. This makes it possible to fix the metal plate to the insulating member more stably.

When the insulating member is separately produced, then is stacked on and fixed to the metal plate, in order to reduce the positional gap between the holes of the insulating member and the metal plate, the hole diameter of the insulating member needs to be larger than the hole diameter of the metal plate.

In contrast, when the insulating member is produced integrally with the metal plate by an insert molding, the process of stacking and fixing the insulating member on and to the metal plate can be omitted, and the difference between the hole diameters of the insulating member and the metal plate may be reduced, and the hole diameter of the insulating member may be smaller than the hole diameter of the metal plate, as compared with when the insulating member is stacked on and fixed to the metal plate. In other words, when viewed in the thickness direction of the metal plate, the portion exposed from the insulating member in the surroundings of the holes of the metal plate can be reduced or eliminated.

First Embodiment

Hereinafter a non-aqueous electrolyte secondary battery as an example of a cylindrical battery according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a vertical cross-sectional view of a non-aqueous electrolyte secondary battery. FIG. 2 is a vertical cross-sectional view of an opening sealing body of FIG. 1. FIG. 3 is a vertical cross-sectional view of a composite body of FIG. 2. FIG. 4 is a plan view of the composite body of FIG. 3. FIG. 5 is a back view of the composite body of FIG. 3.

A non-aqueous electrolyte secondary battery (hereinafter a battery) 10 includes an electrode group 18, an electrolyte (not illustrated), and a bottomed cylindrical battery can 22 that houses these. An opening sealing body 11 is caulking-fixed to the opening of the battery can 22 via a gasket 21. Thus, the battery inside is hermetically sealed.

The opening sealing body 11 includes a valve member 12, a metal plate 13, and an annular insulating member 14 interposed between the valve member 12 and the metal plate 13. The valve member 12 and the metal plate 13 are connected to each other at respective central portions. The insulating member 14 provides insulation between the valve member 12 and the metal plate 13 in the area other than the connection portion between the valve member 12 and the metal plate 13. As illustrated in FIGS. 3 to 5, the insulating member 14 is integrated with the metal plate 13 by an insert molding. In other words, the insulating member 14 and the metal plate 13 form a composite body 19.

For example, aluminum or aluminum alloy is used for the valve member 12 and the metal plate 13. The valve member 12 and the metal plate 13 are produced by machine pressing a plate material such as aluminum into a predetermined shape. The central portion of the valve member 12 and the central portion of the metal plate 13 are connected using, for example, a welding technique such as laser welding.

The valve member 12 is circular when viewed in the thickness direction of the metal plate 13, and has an annular thin-walled portion 12 a which is deformable when the internal pressure of the battery 10 increases. The thin-walled portion 12 a has an inclined area A1 where the thickness of the thin-walled portion 12 a is continuously decreased in the radial direction from the center to the circumferential end face, the inclined area A1 being on the surface, on the inner side of the battery 10, of the valve member 12. Thus, the end, on the circumferential end side, of the valve member 12 in the inclined area A1 serves as a starting point of deformation of the valve member 12 when the internal pressure of the battery 10 increases. The rate of change of the thickness of the thin-walled portion 12 a (the inclined area) may be constant or may be changed from the center to the circumferential end face. When the valve member 12 is viewed in the thickness direction of the metal plate 13, the length (width) of the annular thin-walled portion 12 a (the inclined area A1) in the radial direction equals to, for example, 10 to 80%, preferably 10 to 40% of the radius of the valve member 12.

In the present embodiment, the thickness of the thin-walled portion is continuously decreased from the center to the circumferential end face of the valve member. However, the thickness of the thin-walled portion may be continuously increased from the center to the circumferential end face of the valve member. In this case, the end, on the central side, of the valve member serves as a starting point of deformation of the valve member when the battery internal pressure increases. However, in order to deform the valve member more stably, it is preferable that the thickness of the thin-walled portion be continuously decreased from the center to the circumferential end face of the valve member. Also, although the entire thin-walled portion is the inclined area in the present embodiment, part of the thin-walled portion may be the inclined area.

The metal plate 13 and the insulating member 14 respectively have holes 13 b and holes 14 b which communicate with each other. When the positional gap between corresponding hole 14 b and hole 13 b needs to be prevented, the hole diameter of the hole 14 b is set to be slightly larger than the hole diameter of the hole 13 b as illustrated in FIGS. 3 and 4. In contrast, in the case of an insert molding, positional gap between the holes does not occur, thus the hole diameter of the hole 14 b may be substantially equal to the hole diameter of the hole 13 b, or the hole diameter of the hole 14 b may be smaller than the hole diameter of the hole 13 b unlike FIGS. 3 and 4. In the present embodiment, eight holes 13 b and eight holes 14 b are provided along the circumferential direction. However, the number of holes is not limited to this.

The metal plate 13 is circular when viewed in the axial direction of the battery 10. As illustrated in FIGS. 2 to 5, the metal plate 13 has a thin-walled portion 13 a at its central portion (the connection portion with the valve member). The surface, on the outer side of the battery 10, of the metal plate may have an annular groove (not illustrated) along the circumferential edge of the thin-walled portion 13 a. In this case, when the battery internal pressure reaches a predetermined value, the groove is stably broken. Also, the breaking strength of the groove is easily adjusted.

As illustrated in FIG. 2, the valve member 12 preferably has a protrusion portion 12 c at the central portion of the surface on the inner side of the battery. The protrusion portion 12 c makes it easy to connect the central portion of the valve member 12 and the central portion of the metal plate 13 as well as to dispose the insulating member 14 between the area other than the central portion of the valve member 12 and the area other than the central portion of the metal plate 13. The protrusion portion 12 c is disposed in a hollow portion 14 c of the insulating member 14.

As illustrated in FIG. 2, it is preferable that the valve member 12 further have an annular projection portion 12 d on the circumferential edge of the surface on the battery inner side. The projection portion 12 d makes it easy to fix the composite body 19 to the valve member 12.

An annular groove (not illustrated) may be formed in the valve member 12. In this case, the valve member 12 can operate further stably as an explosion-proof valve. The groove of the valve member 12 may be provided in the thin-walled portion 12 a. The cross-sectional shape of the groove of the valve member 12 preferably has a V-character shape or a U-character shape.

As illustrated in FIGS. 2 and 3, the insulating member 14 has the section P1 that covers the surface, on the valve member side, of the metal plate. The section P1 covers the area other than the central portion (the thin-walled portion 13 a) of the surface, on the valve member 12 side, of the metal plate 13, and has multiple holes 14 b. The insulating member 14 has the section P2 that is provided subsequent to the section P1 and covers the circumferential end face of the metal plate. The insulation distance between the valve member (particularly, the portion on the outer side of the thin-walled portion 12 a) and the metal plate is largely ensured by providing the section P2. When the valve member has the projection portion 12 d as illustrated in FIG. 2, contact between the projection portion 12 d and the metal plate is controlled.

As illustrated in FIGS. 2 and 3, it is preferable that the insulating member 14 further have a section P4 that is provided subsequent to the section P1 and covers the lateral sides of the holes 13 b of the metal plate 13. The insulation distance between the valve member (particularly, the portion on the outer side of the thin-walled portion 12 a) and the metal plate is further largely ensured by providing the section P4.

It is sufficient that the lateral side of at least one of the multiple holes of the metal plate be covered by the section P4. As illustrated in FIGS. 3 and 4, it is preferable that the lateral sides of the multiple holes 13 b be each covered by the section P4. It is sufficient that the section P4 cover at least part (for example, a portion closer to the outer side portion of the thin-walled portion 12 a) of the lateral sides of the holes of the metal plate. The proportion of the lateral sides, covered by the section P4, of the holes of the metal plate is preferably 20 to 90%, and more preferably 40 to 80%.

As illustrated in FIGS. 2, 3, and 5, the insulating member 14 has an annular section P6 that is provided subsequent to the section P2 and the section P4, and covers the surface, on the inner side of the battery 10, of the metal plate 13. In other words, the later-described section P3 and section P5 may be connected. In this case, the metal plate is further stably fixed to the insulating member, thus coming off of the metal plate from the insulating member due to deformation of the opening sealing body at the time of battery crush by pressure, and an internal short circuit (contact between the metal plate and the electrode group or the battery can) caused by the coming off of the metal plate are further controlled.

As illustrated in FIGS. 3 and 5, the surface, on the inner side of the battery 10, of the metal plate 13 may have an area which is not covered by the section P6 and in which the metal plate 13 is exposed, the area being other than the thin-walled portion 13 a. On the surface, on the inner side of the battery 10, of the metal plate 13, it is preferable not to dispose the section P6 and the later-described section P3 and section P5 in at least the area outside the thin-walled portion 13 a and inside the holes 13 b. The area is utilized for connection to the later-described positive electrode lead 15 a.

Instead of the composite body 19 (the insulating member 14) illustrated in FIG. 3, a composite body 39 (an insulating member 34) illustrated in FIG. 6 may be used. The composite body 39 has the same configuration as that of the composite body 19 except that instead of the section P6, a section P3 and a section P5 are provided, the section P3 being provided subsequent to the section P2 to cover the surface, on the inner side of the battery 10, of the metal plate 13, the section P5 being provided subsequent to the section P4 to cover the surface, on the inner side of the battery 10, of the metal plate 13. The section P3 is provided subsequent to the section P2, and the section P5 is provided subsequent to the section P4, and the metal plate is thereby further stably fixed to the insulating member. Thus, coming off of the metal plate from the insulating member due to deformation of the opening sealing body at the time of battery crush by pressure, and an internal short circuit (contact between the metal plate and the electrode group or the battery can) caused by the coming off of the metal plate are further controlled.

The section P3 is provided to cover the area greater than or equal to 0.2 mm from the circumferential end face of the surface, on the inner side of the battery 10, of the metal plate 13 toward the center. In other words, the length L1 illustrated in FIG. 6 is greater than or equal to 0.2 mm. In this case, the metal plate is stably fixed to the insulating member, and coming off of the metal plate from the insulating member due to deformation of the opening sealing body at the time of battery crush by pressure, and an internal short circuit (contact between the metal plate and the electrode group or the battery can) caused by the coming off of the metal plate are controlled. The length L1 illustrated in FIG. 6 is preferably greater than or equal to 0.3 mm. When the insulating member 14 is viewed in the thickness direction of the metal plate 13, the length L1 is, for example, 3% or greater, and preferably 4% or greater of the radius of the metal plate 13. The section P3 may be annular, and may be provided at intervals along the circumferential direction of the metal plate.

It is sufficient that the section P5 cover at least part of the surface, on the inner side of the battery 10, of the metal plate 13, and it is preferable that the section P5 be provided in an annular shape from the section P4 on the surface, on the inner side of the battery 10, of the metal plate 13 toward the circumferential end face. For example, a length L2 of the section P5 illustrated in FIG. 6 is preferably greater than or equal to 0.2 mm, and more preferably greater than or equal to 0.3 mm. The length L2 illustrated in FIG. 6 is, for example, 3% or greater, and preferably 4% or greater of the radius of the metal plate 13.

A recessed portion 12 b is formed by the thin-walled portion 12 a on the insulating member 14 opposing side of the valve member 12. As illustrated in FIGS. 2 to 4, the section P1 preferably has an annular rib 14 a to be housed in the recessed portion 12 b. Because of the inclined area of the thin-walled portion 12 a, the recessed portion 12 b has an inclined face at its bottom, and the rib 14 a has an inclined face corresponding to the bottom of the recessed portion 12 b.

Since the section P1 further has the rib, the amount of resin (thermal capacity) of the insulating member is increased. Thus, it is possible to reduce the risk of melting of the insulating member due to the heat generated by an external short circuit or the like, and contact between the valve member (particularly, the portion on the outer side of the thin-walled portion 12 a) and metal plate is controlled. In addition, since the rib is housed in the recessed portion formed by the thin-walled portion, the insulation distance between the valve member and the metal plate is further largely ensured.

The ratio of the length (width) of the annular rib 14 a in the radial direction to the length (width) of the annular thin-walled portion 12 a (the recessed portion 12 b) in the radial direction as viewed in the thickness direction of the metal plate 13 is, for example, 10% or greater, and preferably 30% or greater.

In the present embodiment, the annular rib 14 a which covers part of the holes 13 b is provided. However, the disposition and the shape of the rib are not limited to this. For example, the rib may be disposed between adjacent holes 13 b of the metal plate 13 at intervals along the circumferential direction. The shape, disposition, and form of the rib may be determined as appropriate according to the shape and position of the recessed portion.

As illustrated in FIGS. 3 and 4, it is preferable that the section P1 have an area A2 which coves part of the holes 13 b (openings) of the metal plate 13, and at least part of the rib 14 a be provided in the area A2. In this case, the insulation distance between the valve member (particularly, the portion on the outer side of the thin-walled portion 12 a) and the metal plate is further largely ensured. When viewed in the thickness direction of the metal plate 13, the proportion of the holes 13 b (openings) of the metal plate 13 covered by the area A2 is, for example, 10 to 80%, and preferably 30 to 60%.

Second Embodiment

Hereinafter, a cylindrical battery according to another embodiment of the present invention will be described with reference to FIG. 7. FIG. 7 is a vertical cross-sectional view of a composite body used in the cylindrical battery according to another embodiment of the present invention. The battery according to the present embodiment has the same configuration as that of the battery 10 illustrated in FIG. 1 except that instead of the composite body 19 (the insulating member 14) illustrated in FIG. 3, a composite body 49 (an insulating member 44) illustrated in FIG. 7 is used.

The composite body 49 includes the metal plate 13 and an insulating member 44. The insulating member 44 has the section P1 that covers the surface, on the valve member side (the battery outer side), of the metal plate 13, the section P2 that is provided subsequent to the section P1 and covers the circumferential end face of the metal plate 13, and the section P3 that is provided subsequent to the section P2 and covers the surface, on the inner side of the battery, of the metal plate. The insulating member 44 (the section P1) has a hole 44 b which communicates with a hole 13 b of the metal plate 13.

The section P3 is provided to cover the area greater than or equal to 0.2 mm from the circumferential end face of the surface, on the inner side of the battery, of the metal plate 13 toward the center. In other words, the length L1 illustrated in FIG. 7 is greater than or equal to 0.2 mm.

In this case, the metal plate is stably fixed to the insulating member, and coming off of the metal plate from the insulating member due to deformation of the opening sealing body at the time of battery crush by pressure, and an internal short circuit (contact between the metal plate and the electrode group or the battery can) caused by the coming off of the metal plate are controlled. The length L1 illustrated in FIG. 7 is preferably greater than or equal to 0.3 mm. When the insulating member 14 is viewed in the thickness direction of the metal plate 13, the length L1 is, for example, 3% or greater, and preferably 4% or greater of the radius of the metal plate 13. The section P3 may be annular, and may be provided at intervals along the circumferential direction of the metal plate.

Hereinafter, the current cut-off mechanism will be described.

When the battery internal pressure increases due to an external short circuit or the like, the valve member 12 receives the pressure through the holes 13 b of the metal plate 13 and the holes 14 b of the insulating member 14, and the thin-walled portion 12 a of the valve member 12 is deformed. Accordingly, the central portion of the valve member 12 is pulled outwardly of the battery along with the central portion of the metal plate 13. When the battery internal pressure reaches a predetermined value, the annular groove (not illustrated) provided in the surroundings of the connection portion of the metal plate 13 with the valve member 12 is broken, and a current path between the valve member 12 and the metal plate 13 is cut off.

In the case where the metal plate 13 has no groove, a configuration may be adopted in which when the battery internal pressure reaches a predetermined value, the connection portion (welded portion) between the metal plate 13 and the valve member 12 is broken (a configuration in which the central portion of the metal plate 13 is detached from the central portion of the valve member 12). The breaking strength of a groove of the metal plate is easier to be adjusted than the breaking strength of the connection portion (welded portion), thus the metal plate 13 preferably has a groove in the surroundings of the connection portion with the valve member 12. The cross-sectional shape of the groove of the metal plate 13 preferably has a V-character shape or a U-character shape.

A positive electrode lead 15 a drawn from a positive electrode plate 15 is connected to the metal plate 13. Thus, the valve member 12 functions as an external terminal of the positive electrode. A negative electrode lead 16 a drawn from a negative electrode plate 16 is connected to the bottom internal surface of the battery can 22.

For example, iron, iron alloy, stainless steel, aluminum, and aluminum alloy are used as the material for the battery can 22. An annual groove 22 a is formed in the vicinity of the opening end of the battery can 22. A first insulating plate 23 is disposed between one end face of the electrode group 18 and the annual groove 22 a. A second insulating plate 24 is disposed between the other end face of the electrode group 18 and the bottom of the battery can 22.

The electrode group 18 is formed by winding the positive electrode plate 15, the negative electrode plate 16, and a separator 17 interposed therebetween.

The positive electrode plate 15 includes a foil positive electrode current collector, and a positive electrode active material layer formed on its surface. For example, aluminum, aluminum alloy, stainless steel, titanium, and titanium alloy are used as the material for the positive electrode current collector. A lithium transition metal composite oxide is preferably used as the positive electrode active material. For example, a composite oxide is used, which includes at least one type selected from a group and lithium, the group consisting of cobalt, manganese, nickel, chromium, iron, and vanadium.

The negative electrode plate 16 includes a foil negative electrode current collector, and a negative electrode active material layer formed on its surface. For example, copper, copper alloy, nickel, nickel alloy, and stainless steel are used as the material for the negative electrode current collector. A carbon material which can reversibly occlude and discharge lithium ions, for example, natural graphite, artificial graphite, hard carbon, soft carbon, tin oxide, and oxide silicon may be used as the negative electrode active material.

For example, a microporous membrane composed of polyolefin may be used as the separator 17. As polyolefin, polyethylene, polypropylene, and ethylene-propylene copolymer may be exemplified.

The electrolyte includes a non-aqueous solvent, and lithium salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, a cyclic carbonate such as an ethylene carbonate, a propylene carbonate, and a butylene carbonate, a chain carbonate such as a dimethyl carbonate, a diethyl carbonate, and an ethyl methyl carbonate, a carboxylic acid ester, and a chain ether are used. As the lithium salt, LiPF₆, LiBF₄, LiClO₄, and the like are used.

INDUSTRIAL APPLICABILITY

The cylindrical battery according to the present invention is useful as a small-sized electronic device such as a notebook personal computer, a power tool for an electric tool and an electric power-assisted bicycle, and a driving power source for an electric automobile.

REFERENCE SIGNS LIST

-   -   10 NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY     -   11 OPENING SEALING BODY     -   12 VALVE MEMBER 12 a THIN-WALLED PORTION     -   12 b RECESSED PORTION     -   12 c PROTRUSION PORTION     -   12 d PROJECTION PORTION     -   13 METAL PLATE     -   13 a THIN-WALLED PORTION     -   13 b HOLE     -   14, 34, 44, 54 INSULATING MEMBER     -   14 a RIB     -   14 b, 44 b HOLE     -   14 c HOLLOW PORTION     -   15 POSITIVE ELECTRODE PLATE     -   15 a POSITIVE ELECTRODE LEAD     -   16 NEGATIVE ELECTRODE PLATE     -   16 a NEGATIVE ELECTRODE LEAD     -   17 SEPARATOR     -   18 ELECTRODE GROUP     -   19, 39, 49 COMPOSITE BODY     -   21 GASKET     -   22 BATTERY CAN     -   22 a GROOVE     -   23 FIRST INSULATING PLATE     -   24 SECOND INSULATING PLATE     -   55 HOOK PORTION 

1. A cylindrical battery comprising: an electrode group; an electrolyte; a battery can that houses the electrode group and the electrolyte; and an opening sealing body that seals an opening of the battery can, the opening sealing body including a valve member, a metal plate disposed on an inner side of the battery with respect to the valve member, and an annular insulating member interposed between the valve member and the metal plate, wherein the valve member and the metal plate are connected to each other at respective central portions, the valve member has a thin-walled portion which is deformable when an internal pressure of the battery increases, the insulating member has a section P1 that covers a surface, on the valve member side, of the metal plate, a section P2 that is provided subsequent to the section P1 and covers a circumferential end face of the metal plate, and a section P3 that is provided subsequent to the section P2 and covers a surface, on an inner side of the battery, of the metal plate, and the section P3 is provided to cover an area greater than or equal to 0.2 mm from the circumferential end face of the surface, on the inner side of the battery, of the metal plate toward a center.
 2. The cylindrical battery according to claim 1, wherein the metal plate and the insulating member have respective holes which communicate with each other.
 3. The cylindrical battery according to claim 2, wherein the insulating member further has a section P4 that is provided subsequent to the section P1 and covers a lateral side of the holes of the metal plate.
 4. The cylindrical battery according to claim 3, wherein the insulating member further has a section P5 that is provided subsequent to the section P4 and covers the surface, on the inner side of the battery, of the metal plate.
 5. The cylindrical battery according to claim 1, wherein a recessed portion is formed by the thin-walled portion on the insulating member opposing side of the valve member, and the section P1 has a rib to be housed in the recessed portion.
 6. The cylindrical battery according to claim 5, wherein the section P1 has an area which covers part of the holes of the metal plate, and at least part of the rib is provided in the area.
 7. The cylindrical battery according to claim 1, wherein the insulating member is integrated with the metal plate by adhesive bonding. 